1. Field of the Invention
The present invention relates to a fin and tube type heat exchanger, and more particularly, to a fin tube heat exchanger of a compact type, for reducing a production cost, enhancing a heat exchange efficiency compared to a related art heat exchanger, and reducing power consumption of a motor coming from a pressure loss.
2. Background of the Related Art
FIGS. 1 and 2 illustrate fin tube type heat exchangers. The fin tube type heat exchanger is provided with a plurality of fins stacked perpendicular to heat exchange tubes 10, to enlarge a heat exchange surface for enhancing a heat exchange effect. There are a plurality of coupling holes 21 in a surface of the fin along a long side direction of the cooling fins 20, through which the heat exchange tubes 10 are passed. The coupling holes are formed in two rows in zigzag in an upper step and in a lower step of the cooling fins. A space between adjacent coupling holes 21 on the same step is opened for an air flow(a short side direction of the cooling fin), and the space has a plurality of projections 22 formed reciprocally in a front and a rear surfaces thereof for guiding the air flow that passes respective cooling fins. Therefore, the refrigerant flowing in from a refrigerant inlet of the heat exchange tubes 10 passes inside of the heat exchange tubes, to cool down the heat exchange tube 10 and drop a temperature of the heat exchange tubes, and, on the same time with this, a heat source (air) provided from outside of the heat exchanger is passed between the cooling fins 20 by rotation of a fan(not shown), so that the air passed between respective cooling fins makes heat exchange with the refrigerant through the heat exchange tubes 10, the cooling fins 20 and the projections 22. And, the turbulence caused by the projections 22 as the air hits onto the projections 22 during the air passes through openings of the projections 22 enhances the heat exchange effect.
In the meantime, design criteria of the aforementioned related art heat exchanger are fixed to maximize the heat exchange efficiency. Taking the fact that a thermal resistance on a side external air flows is higher than a thermal resistance inside of the heat exchange tube into account, a difference of the thermal resistances can be reduced by enlarging a heat exchange surface on the side the external air flows. For this, a center distance between adjacent coupling holes 21 on the same row in the cooling fin 20 (called as "step pitch S") is set in terms of the tube diameter D.sub.0 to be 2.5 D.sub.0.ltoreq.S.sub.1.ltoreq.3.0 D.sub.0 and a width of the cooling fin 20(or a distance between adjacent steps when the cooling fin has at least two steps of the coupling holes)(called as "row pitch L.sub.1, ") is set in terms of the tube diameter D.sub.0 to be 1.2 D.sub.0.ltoreq.L.sub.1.ltoreq.1.8 D.sub.0. Considering that generally used diameters of the tube 10 are 9.52 mm or 7 mm, the heat exchanger with the tube diameter D.sub.0 9.52 mm is designed to have the step pitch S.sub.1 to be within a range of 2.5.about.2.7 D.sub.0 and the row pitch L.sub.1 to be in a range of 1.8 D.sub.0. And, the heat exchanger with the tube diameter D.sub.0 7 mm is designed to have the step pitch S.sub.1 to be in a range of 3 D.sub.0 and the row pitch L.sub.1 to be in a range of 1.2 D.sub.0. As the foregoing configurations of the heat exchanger has small ranges of the step pitches S.sub.1 and the row pitches L.sub.1, compared to the tube diameters D.sub.0, an improvement of the heat exchange performance can be achieved when an air flow rate is the same.
However, the small ranges cause a higher pressure loss on the air side. That is, the high air flow speed required for the improvement of the heat exchange performance causes an increased noise, but a configuration of the tubes designed to reduce the noise drops the heat exchange performance. Because a power of a fan motor (not shown) should be increased for obtaining the same air flow rate in a state the pressure loss on the air side is increased, a power consumption can not, but be increased, and damage to the fan motor can be caused.